1. Field of the Invention
The present invention relates to a semiconductor module, particularly to a heat sink for a semiconductor module used as an extended or expanded memory module in a personal computer or the like. Also, the present invention relates to a semiconductor module in which the above-mentioned heat sink for a semiconductor module is incorporated.
2. Description of the Related Art
First, the structure of a semiconductor module, especially that generally used as an extended or expanded memory module in a personal computer or the like, will be described with reference to FIG. 14.
A memory module 10 is comprised of a circuit board 12 having a plurality of terminals 11 formed along an edge thereof, and a plurality of semiconductor memories 14 mounted on both surfaces of the circuit board 12. The semiconductor memory 14 may be mounted in various ways. For example, a memory element (memory chip) itself which is a semiconductor element is directly carried on the circuit board by a flip-chip method or others, or the memory element may be packaged with resinous material together with a lead frame to form a semiconductor device which is then mounted onto the circuit board. Alternatively, the semiconductor memory may be of a chip-size package type such as .mu. BGA.
Next, a structure of a prior art heat sink used in this memory module 10 as well as an attachment structure therefor will be described with reference to FIGS. 14 to 16.
A heat sink 16 is constructed by a pair of metallic plates 18, each formed to have a generally rectangular contour similar to that of the circuit board 12 and have a size sufficient for covering an overall area in the circuit board 12 mounting the semiconductor memories 14 thereon. A recess 20 is formed in the respective metallic plate 18, having dimensions capable of receiving the semiconductor memory 14 of a certain thickness attached to the surface of the circuit board 12 so that an inner surface of the metallic plate 18 is brought into close contact with a back surface of the semiconductor memory 14 when the metallic plates 18 is brought into close contact with the both sides of the circuit board 12, respectively.
The heat sink 16 is attached to the circuit board 12 while using a plurality of through-holes 24 provided at positions corresponding to a plurality of (e.g. four) attachment holes 22 provided in the circuit board 12.
The heat sinks 16 are arranged on the respective sides of the memory module 10 so that all of the through-holes 24 provided in the respective heat sink are aligned with the respective attachment holes corresponding thereto.
Then, a rivet 26 is inserted into the through-hole 24 of the heat sink 16 and the attachment hole 22 thus aligned to each other, while projecting opposite ends of the rivet 26 out of the holes 22, 24. The projected ends are hammered to have a larger diameter. Thereby, the heat sinks 16 are attached to the both surfaces of the memory module 10.
However, there is a problem when the heat sinks 16 are attached to the memory module 10 in the above-mentioned manner, in that the operation is extremely troublesome, for bringing the heat sinks 16 into close contact with the circuit board 12 of the memory module 10 via a tape 28 while positioning the through-holes 24 to the attachment holes 22 corresponding thereto and inserting the rivets 26 one by one into the respective through-holes 24 aligned with the attachment holes 22, after which the projected ends of the rivet are hammered to secure the heat sink 16 to the memory module 10.
This is because there is no positioning mechanism between the circuit board 12 and the heat sink 16, whereby the alignment between both the holes is liable to be disturbed, by a trifling cause, to prevent the rivets 26 from being inserted.